It is the long-term objective of this laboratory to improve functional outcome after spinal cord injury (SCI). One important issue is the chronic pain sensations that the majority of patients with SCI experience. This project focuses on the development of a mammalian model of chronic central pain that is reproducible and has both spontaneous and evoked pain components, an important contribution which will allow an investigation of mechanisms and possible therapeutic interventions. There are four hypotheses to be tested: 1. Spinal cord injury produces chronic pain which can be measured as alterations in evoked behaviors. 2. Excitatory amino acids (EAA) and peptides play important roles in the alterations of evoked somatosensory behavior observed after spinal cord hemisection. 3. EAAs and peptides play an important role in central sensitization of dorsal horn neurons in nociceptive pathways in this SCI model. 4. Spinal cord injury produces chronic pain which can be measured as alterations in spontaneous, non-evoked behavior. Methods include behavioral tests, electrophysiological recordings, microdialysis and behavioral outcome of pharmacological intervention. These data will contribute toward understanding the symptomology and behavioral changes characteristic of partially spinalized patients.